In recent years book binding systems which perform continuous steps from image formation to book binding using an electrophotographic type image forming apparatus have been developed and are being used.
This type of book binding system is required to be small in size since it is used in offices or other locations similar to the office environment. For this reason, adhesion processing devices which have bonds such as those in Patent Documents 1 and 2 are widely used as a processing apparatus in which a plurality of sheets are stacked to form a booklet.
Patent Documents 1 and 2 disclose a technique in which, when the spine of a plurality of sheets is coated with adhesive and the papers are bonded together to form a booklet, the coating frequency is changed in accordance with the thickness of the booklet and thus booklets of different thickness have a prescribed adhesive strength.
[Patent Document 1] Unexamined Japanese Patent Application Publication No. 2000-168265
[Patent Document 2] Unexamined Japanese Patent Application Publication No. 2004-209753
In adhesion processing with bond, there is a problem in that adhesive strength varies depending on the type of paper.
Adhesion processing with bond includes the process of stacking and aligning a plurality of sheets of paper to thereby line up the spines of the sheet stack and applying adhesive to the spine using a coating section such as a coating roller or the like.
In regular paper, it is easy to infuse into the paper with the adhesive, and also a suitable space is formed between the sheets of paper and this space becomes infused with adhesive. For this reason, in regular paper, even with a small amount of adhesive, the sheets can be bonded to each other with high adhesive strength.
Meanwhile, in coated paper or high quality paper, it is difficult for the paper to be infused with adhesive due to the quality of the paper and the smoothness of the surface, and the spine of the paper stack that have been aligned is flat with little unevenness, and because it is difficult for space between the sheets of paper to become infused with adhesive, the adhesive strength is sometimes insufficient.
As is the case in Patent Documents 1 and 2, by only changing coating frequency in accordance with booklet thickness, booklets which have different adhesive strength depending on the type of paper are created and this is problematic in terms of insufficient strength and excess coating.